This issue may very well correct itself with time, but for the record I'd like to indicate that even though the LGV Mediterranée route is out, its Xbox Live achievements are not available nor unlockable. It's possible that a title update is needed for the TSW 2 main game for the achievement list to be expanded. If so, this update is not out at the time of writing this. If the achievement list doesn't become available today then it would probably be a good idea to look after it. But hopefully it will sort itself out soon.
I'd just like to reiterate that after the 1.0.201.0 update for both the main game and LGV, the achievements are still not live.
dreampage Appreciate you highlighting this, we will look into it and find out why that wasn't resolved with the most recent update.